Manufacture of rubber articles



UNITED STATES PATENT OFFICE 1,959,556 MANUFACTURE OF RUBBER ARTICLES Geoffrey William Trobridge, Sutton Coldfield, England, assignor to Dunlop Rubber Company Limited, London, England, a British company No Drawing. Application October 17, 1932, Serial No. 638,185. In Great Britain November 26, 1931 Claims. (Cl. 18-58) My invention relates to improvements in the thesupports or backing strata can be effected by manufacture of articles of rubber or similar mathe application of heat, or by the application of terial by forming deposits thereof from suitable coagulants, or by dehydrating and setting means, aqueous dispersions on supports or backing strata. or by combinations of these various means.

5 The invention relates more particularly to the Where a former is used, it can be internally o0 formation of thin deposits of rubber. heated during the immersion in the aqueous dis- In the production of thin rubber articles it is persion, or subsequent thereto, or both during usually extremely difiicult to produce a thin immersion and subsequently thereto. Articles of walled article free from bubbles which cause deappreciable thickness may be made by successive fects in the finished article, and to produce an thinner coatings. 65 article of the desired uniformity of wall thick- The various coating compositions may be apness. The production of thin walled articles plied in any of the usual operations such as dipfi'om aqueous dispersions is also rendered more ping, pouring, spreading or spraying, and the difiicult in many cases because it is not practicable supporting surface or former may be of various in such cases to use a coagulant. materials such as glass, metal, porcelain, hard or m An object of my invention is to provide a methsoft rubber, clay or fabric. The term rubber is 0d of forming rubber articles from aqueous dis used in its broadest significance as including natpersions in which bubbles in the deposited rubber ural or artificial aqueous dispersions of India rubmaterial may be readily avoided, and in which her, or similar vegetable resins such as gutta uniformity in wall thickness and structure may percha or balata with or without the addition of 7 b obtained, aqueous dispersions or emulsions of rubber-like In my invention the surface on which the desubstances such as synthetic rubbers, mineral posit of rubber material is to be made is first rubbers or rubber substitutes such as factice or coated with a non-coagulating composition comrubber reclaim, or rubber waste or oils, for exprising one or more polyhydroxy compounds, or ample, rape oil or vulcanized oils or cellulose other derivatives, in admixture with a volatile esters or proteins, for example, casein. The dissolvent. The aqueous dispersion is then brought persions may be concentrated or compounded, or into contact with the thus treated surface to coat both compounded and concentrated. A comthe latter and the deposit or coating thus formed pounded concentrate such as described in Patent 30 i thereafter l t d, 1,846,164 is suitable. The compounding ingredi- The polyhydroxy compounds used in coating ents may comprise vulcanizing agents such as the surface are such as have a slight stabilizing Sulphur, Organic c l ators and reinforcing action on the dispersion. Polyhydric alcohols, agents Such as Whiting, Clay, barium p a or other derivatives, such as glycerol, glycol, dihthopone, 1? black, gas a k,'zi nc oxide or 35 ethylene glycol or alkyl ethers of these, such as 9 Vulcamte, colormg matters glycol monoethyl ether, are examples of suitable preservatlves Softeners;- polyhydroxy compounds, An example of carrying the invention into These polyhydroxy compounds may bemixed efiect is as follows:

with any suitable volatile solvent such as acetone, Example I 40 alcohol or ether.

AS an example of a noncoagulatmg composl' A non-coagulating composition suitable for the h h y P used according to the present production of thin rubber dipped goods from invention is a mixture of glycerme and alcohol. rubber latex, Such as finger cots, can be made as The glycerine appears to facilitate wetting by follows;

the aqueous dispersion aforesaid and also to act Parts by as a slight stabilizer, in this manner, apparently, weight preventing the coagulation of the deposit until Glycerine 5 the forces of the surface tension have compen- 95% alc hol 95 50 sated for any slight inequality of deposition. The alcohol while completely wetting the former, ap- This composition is then wiped over a former,

pears to act also as a quickly evaporating diluent for instance of glass, by means of a cloth so as for the glycerine, thereby enabling a very thin to produce a coating thereof. The thus coated application of the glycerine to be made uniformly. former is allowed to stand for about one minute The subsequent coagulation of the deposits on until the alcohol has evaporated. This is then dipped into a latex bath of 55-60% total solids of the following composition:

The former with the liquid film of latex mixing is then removed from the bath. On withdrawal the former is rotated so as to obviate variations in thickness of deposit, and is then carefully inverted and placed over'a jet of steam so that the former is internally heated.

The dried deposit is then suitably treated in any known manner, e. g., vulcanized in steam for ten minutes at 15 lbs. pressure per square inch.

Through the above invention a smooth, uniform deposit, free from bubbles, is obtained through the action of the glycerine or other polyhydroxy compound in causing the dispersion to wet the forming surface uniformly and to revent coagulation until the deposit will have had an opportunity to become uniformly distributed.

What I claim is- 1. A method for the production of articles from aqueous dispersions of rubber which comprises coating a supporting surface with a non-coagulating composition comprising polyhydroxy organic compounds in admixture with a volatile solvent, evaporating solvent from said coating, coating the thus treated supports with an aqueous dispersion of rubber, and coagulating the coating.

2. A process as in claim 1 in which the polyhydroxy compounds are polyhydric alcohols.

3. The process as claimed in claim 1 in which the volatile solvent is a member of the group consisting of acetone, alcohol and ether.

4. The method of claim 1 in which the noncoagulating composition is a mixture of glycerine and alcohol.

5. The process as claimed in claim 1 in which the supporting surface is internally heated.

GEOFFREY WILLIAM TBOBRIDGE. 

